Motor control system and method for protecting inrush resistor

摘要

A system for protecting an inrush resistor by determining whether an inrush relay connected in parallel with the resistor properly closes. A differential amplifier connected across the resistor produces an output signal that is proportional to the differential voltage. A control circuit determines whether the relay is open based on the output signal, and if the relay is open and the motor is running, takes remedial action to protect the inrush resistor. Alternatively, the amplifier is replaced with a slow response filter that produces an output signal that is a delayed version of a bus voltage. The control circuit determines the difference between the bus voltage and the output signal, and if it exceeds a predetermined value and the motor is running, takes remedial action to protect the inrush resistor. Remedial action may include shutting off the motor or restarting the motor to confirm improper behavior of the relay.

主权项

1. An electric motor system comprising:
an electric motor; and a motor control subsystem operable to control operation of the electric motor, the motor control subsystem including—
a power inverter operable to receive power from a power source and to convert the power to drive the electric motor,an inrush resistor electrically connected in series with the power source and operable to ameliorate an initial increase in an electric current during charging of a bus capacitor prior to starting the electric motor,an inrush relay electrically connected in parallel with the inrush resistor and operable to close after the bus capacitor is charged and thereby direct the electric current around rather than through the inrush resistor,a differential amplifier electrically connected across the inrush resistor and operable to sense a differential voltage across the inrush resistor and to produce an output voltage signal that is proportional to the differential voltage, anda control circuit in communication with the differential amplifier and operable to determine whether the inrush relay is open based on the output voltage signal of the differential amplifier, and if the inrush relay is open and the motor is running, to take remedial action to protect the inrush resistor.